Food allergy and food anaphylaxis are debilitating and life threatening conditions. In order to better understand the molecular mechanisms underlying food anaphylaxis, our laboratory has extensively studied a murine model of oral allergen-induced IgE-dependent intestinal anaphylaxis (1). Interestingly, we recently uncovered that this model was characterized by an increased expression of the secreted protein TSG6 mRNA, tumor necrosis factor induced gene 6. At the same time, we also discovered that TSG6 mRNA was upregulated in a human food allergy related disease, eosinophilic esophagitis (EE) (2). Taken together, these sets of observations have focused our attention on uncovering the role of TSG6 in food allergy related responses. TSG6 is a potent inhibitor of neutrophil recruitment;some studies have indirectly associated TSG6 to lymphoid cell adhesion and activation through its propensity to increase binding to hyaluroan (6-8);and TSG6 increases protease activity. Our present study will focus on understanding the expression and role of TSG6 in food allergy-related responses in mice and humans. Aim I: To characterize TSG6 expression in murine and human food allergy related responses. In this aim, we hypothesize that TSG6 mRNA and protein levels will be upregulated during induction of experimental intestinal anaphylaxis, experimental EE, and human EE. We will define the kinetics and cell types that express TSG6 in both systems. Real-time PCR and ELISA will be used to quantify the mRNA and protein expression in mice. Immunohistochemistry, in situ hybridization, and flow cytometry analysis will be carried out to identify the TSG6 expression pattern in the gastrointestinal tract. Aim II: To define the role of TSG6 in vivo in experimental intestinal anaphylaxis. In this aim, we hypothesize that TSG6-deficient mice will develop attenuated Th2-associated diseases, i.e., a delay in diarrhea occurrence. Accordingly, we will assess a variety of clinical, pathological, and immunological endpoints using ELISA, flow cytometry, and tissue staining techniques. Aim III: To define the role of TSG6 in experimental EE. In this aim, we hypothesize that TSG6 will promote the development of EE, especially in eosinophil recruitment and tissue remodeling while inhibiting neutrophilic inflammation. TSG6-deficient mice will be subjected to experimental EE and the development of adaptive and innate immune responses will be assessed, as well as tissue remodeling using ELISA, immunohistochemistry, and protease activity assays. Potential impact: We are hopeful that this study will unravel new molecular mechanisms involved in IgE- mediated inflammation and will help provide a better understanding of the disease. We believe that this study will be a milestone in the development of new therapeutic approaches aiming to target TSG6 for IgE-mediated food allergy related diseases. Food allergy and food anaphylaxis are debilitating and life threatening conditions. The overall goal of these grant application is to uncover the role of TSG6 in food allergy related responses.